1. Field of the Invention
This invention relates to a digital image data recording apparatus inclusive of a digital video tape recorder (DVTR) and digital camera, etc., a method of recording digital image data in a DVTR, an apparatus and method for reproducing digital image data that has been recorded on a magnetic tape by the DVTR or recording method, as well as a solid-state electronic image sensing device and a method of reading a signal charge out of the solid-state electronic image sensing device.
2. Description of the Related Art
A digital video tape recorder (DVTR) senses the image of a subject using a solid-state electronic image sensing device such as a CCD, converts a video signal, which represents the image of the subject obtained by image sensing, to digital image data and records the digital image data on magnetic tape. A CCD used in a DVTR generally has about 350,000. pixels in an array of 720 pixels horizontally and 480 pixels vertically. A signal charge that accumulates in the solid-state electronic image sensing device used in the DVTR represents the image of the subject. The signal charge can be read out of the device by non-interlaced readout (readout of all pixels) and by interlaced readout (movie readout).
In non-interlaced readout, all of the signal charge that has accumulated in the solid-state electronic image sensing device is outputted at a period of 1/30 of a second. Accordingly, non-interlaced readout makes its possible to obtain a high-quality image of a subject and is a method of readout that is suitable for situations in which the reproduction of still pictures is considered. In interlaced readout, output of signal charge that has accumulated in odd-numbered rows of photoelectric transducers in the solid-state electronic image sensing device and output of signal charge that has accumulated in even-numbered rows of the photoelectric transducers alternate every 1/60 of a second. Interlaced readout makes it possible to shorten the signal-charge output period in comparison with non-interlaced readout and is a method of readout that is suitable for situations in which reproduction of moving pictures is considered.
With non-interlaced readout, one frame is composed of two fields and frame recording for recording a frame image is performed. According to interlaced readout, field recording which records a field image for every field is carried out. In both frame recording and field recording, one frame of image data is recorded on magnetic tape over a time of 1/30 of a second and using a recording area composed of ten tracks.
Thus, in a digital video tape recorder, one frame of image data of the digital image data obtained by photographing a subject using a 350,000-pixel CCD generally is recorded on ten tracks over a period of 1/30 of a second. This recording scheme is the standard in industry (For example, see NIKKEI ELECTRONICS BOOKS, "Data Compression and Digital Modulation", pp. 137-152, Nikkei BP Sha, 1993).
The image quality in the image sensing section of the digital video tape recorder depends upon the number of pixels in the CCD; the larger the number of CCD pixels, the greater the improvement in image quality. However, in order for image data obtained from a CCD to be recorded on magnetic tape using a CCD having a large number of pixels for the sake of improving image quality, the recording of the image data requires more than 1/30 of a second and a recording area of more than ten tracks. This is not in conformity with the above-mentioned standard established for a digital video tape recorder.
In a case where the image sensing section of a DVTR uses a CCD having more pixels than the approximately 350,000 pixels employed conventionally, there is a need for interlaced readout and non-interlaced readout suited to such a CCD.